Air drying composition of the alkyd resin type



Patented Dec. 22, 1936 UNITED STATES AIR name COMPOSITION OF 'rrm ALKYDRESIN ma Howard L. Bender, Bloomfield, N. J., asaignor to BakeliteCorporation, lwration or Delaware New York, N. 'Y., a cor- No Drawing.Application July 11, 1933, Serial No. 679,991

4 Claims.

This invention relates to synthetic resinous compositions that areprimarily intended for use as coatings or impre'gnations and have theproperty of drying in air to commercially usable films for theprotection of structural parts, oar bodies, implements, etc. fromatmospheric efiects, where the conditions of use or application aresuch-that an after-heating or baking of the films is impractical orimpossible.

The synthetic resinous compositions with which this invention isconcerned are differentiated from natural or other resins by an initialor potentially reactive or soluble and fusible A stage and gradu; allyconvertible or hardenable by heat to a final infusible insoluble'or Cstage. These resinous compositions include the phenolic aldehyde, theglycerol-polybasic and the urea' or thin-ureaaldehyde products; and todistinguish. them from the permanently fusible soluble resins, the termresinold has been adopted and is so used herein.

In a prior application Serial No. 636,955 filed' October 8, 1932 nowPatent 1,922,272 there is more particularly described and claimedresinold compositions of the phenolic type. The present applicationwhich is a continuation-in-part of the above mentioned application isspecifically -drected to resinoids of the polyhydric alcoholpolybasicacid type and sometime designated as alkyd resins. varnishes preparedtherefrom deposit films or coatings which, upon evaporation of thevolatile content, are non-tacky, adhere firmly to the base material andhaving a pleasing homogeneous translucent appearance; furthermore, thefilms 'or coatings show a marked resistance to sunlight, waterpenetration and weak alkaline or soap solutions. An additionalcharacteristic of these varnishes and of manifest im-; portance is thecomparative ready release of sufficient solvents from the film formingbody with the consequence that a film dries to a non-tacky condition ina surprisingly short period of time. In order that the present inventionmay be fully disclosed, a specific example relating to the preparationof varnishes follows, but it is to be understood that the conditions andproportions are illustrative only and are subject to changecommensur'ate in scope with the appended claims.

Example.-A resinold of the polyhydric alcoholpolybaslc acid type isobtained by reacting 92 parts or 1 mol. of glycerine with 184 parts orfrom 13 to 1 mols of phthalic anhydride until the temperature reaehesabout 200 to 220 0.; the water is allowed to escape until a sample showsa resin which is solid when cold, or with the above proportions untilabout 36 parts of water have been driven off. Then 50 parts of diethyloxylate, glycol diacetate or other known suitable medium boiling pointsolvents or high boiling point solvents, such-as the high boilingketones, the diethyl or dibutyl esters of phthalic, tartaric 5 orsimilar organic acids, is added and the mass is refluxed until a sampleshows a liquid condition at about 180 C. but gels upon cooling. At thispoint suflicient volatile solvent, as for example 200 parts of acetone,cellosolve (monoethyl ether 'of ethylene glycol), or their mixtures withalcohol, etc. are added to make a varnish of about 50 per cent solidcontent. The varnish if of low viscosity is refluxed until a sampleshows a viscosity of 500 centipoises or more measured in 50 per centsolution. The varnish so made, when tested is found to benon-penetrating or but slightly penetrating when applied to kraft paper.Glycol or polyglycerhie may be used to replace all or-part of theglycerine and -any dibaslc or polybasic organic acid or acid anhydridemay be used in place of phthalic anhydrid'e; monobasic organic acids,particularly those of the fatty acid groups having some unsaturatedcarbons present, may be substituted for part of the polybasic acid.Acids, such as sebacic and adipic, may be included to give specialproperties such as increased flexibility.

In the step of refluxing the resinold while dissolved in diethyl oxalateor other known suitable solvent there is an advancement of the resinoldtoward a hardened or polymerized'condition indicated by a liquidcondition when hot and a gelling of a sample when cold. The furtherrefluxing in the presence of volatile solvent causes additionalpolymerization or hardening as shown by the increase in viscosity.

The extent of advancement or degree of polymerization of the resinoldfound desirable has no well defined critical limits except that gellingof 40 the mass as a'whole is to be avoided. In general the viscosity at500 centipoises in the finished varnish when adjusted to a per centsolid content'is indicative of 'suflicient advancement to insure thedeposition of a. film having requisite 45 toughness and durability upondrying in air. Such a varnish shows substantially no penetration whenapplied to kraft paper of 5 mils thickness. Since the resinold in thereacted or advanced condition is insoluble for all practical purposes ina solvent such as acetone, the advancement in such a solvent resultslargely in a colloidal suspension or dispersion, the extent of which ismanifested by the lack of penetration. This colloidal condition isfurther evidenced by the F fact that, although the solvent and thecontained resinoid when sufliciently advanced by heating may have theappearance of a true solution, further additions of the same solventresult in a precipitation of the resinoid.

While this invention 'is not limited as to the solvents which can beused, it v is particularly adapted to the use and inclusion of highboiling solvents which remain in the final product, and such solventsand plasticizers can therefore be chosen as will impart plasticity andflexibility or other desirable qualities to the film or coating as wellas render possible the advancement of the resinoid therein. A list ofsolvents for this purpose includes'most of the well-known plasticizersing a volatile solvent in proportion to form a varnish of about 50 percent solid content and refluxing the varnish to a viscosity of about 500centipoises or more.

2. Process of preparing coating compositions drying in air byevaporation of solvent to a nontacky film, which comprises reacting apolyhydric alcohol with a polybasic acid to the point where a samplesolidifies when cold, adding a high boiling solvent, refluxing thesolution until a sample in a liquid condition at about 180 C. gels uponcooling, adding a volatile solvent to form a varnish and refluxing thevarnish until. it shows a, viscosity of at least 500 centipoises whenadjusted to a solid content of 50 per cent.

3. Process of preparing a coating composition which comprises reacting apolyhydric alcohol with a polybasic acid to the point where a samplesolidifies when cold, and refluxing the reaction product in the presenceof a. solvent until it shows a viscosity of at least 500 centipoiseswhen adjusted to a solid content of 50 percent, thereby producing acomposition which deposits a nonta'cky film upon evaporation of solvent.

4. A liquid coating composition comprising a resinoid of the polyhydricalcohol-polybasic acid type and a solvent medium, the resinoid beingadvanced to a condition such that the composition shows a viscosity ofat least 500 centipoises "when adjusted to a solid content of 50percent,

the composition being substantially non-penetrative when applied tokraft paper and depositing a non-tacky film upon evaporation of solvent.

HOWARD L. BENDER.

